Drop-on-demand ink jet printers use thermal energy to produce a vapor bubble in an ink-filled chamber to expel a droplet. A thermal energy generator or heating element, usually a resistor, is located in the chamber on a heater chip near a discharge orifice. A plurality of chambers, each provided with a single heating element, are provided in the printer's printhead. The printhead typically comprises the heater chip and an orifice plate having a plurality of the discharge orifices formed therein. The printhead forms part of an ink jet print cartridge which also comprises an ink-filled container.
The resistors are individually addressed by energy pulses provided by a printer energy supply circuit. Each energy pulse is applied to one of the resistors to momentarily vaporize the ink in contact with that resistor to form a bubble which expels an ink droplet. A flexible circuit is used to provide a path for the energy pulses to travel from the printer energy supply circuit to the printhead. The flexible circuit includes a substrate portion and a plurality of traces located on the substrate portion. The traces have end sections which extend out from the substrate portion. The extending sections are coupled to bond pads on the printhead. Typically, there is a first row of coupled bond pads and trace sections and an opposing, second row of coupled bond pads and trace sections.
It is known in the art to form a barrier layer over each row of coupled bond pads and extending trace sections. One known process for forming such a barrier layer involves dispensing an encapsulant material onto the coupled bond pads and trace sections using a discharge needle.
Once a barrier layer has been formed over each row of coupled bond pads and extending trace sections, an inspection is made to determine if each barrier layer is properly positioned on the print cartridge. If one of the barrier layers is improperly positioned on the print cartridge, the layer may block one or more of the orifices. Also, if the spacing between the two barrier layers is too narrow, wiping of the orifice plate surface may be made more difficult.
One known method for conducting an inspection for proper barrier layer placement involves measuring the distance from a center portion of the orifice plate to an inner edge of the barrier layer. If the distance is less than a predetermined value, then the barrier layer is improperly located and the print cartridge is unacceptable. Such an inspection is not easily accomplished in a high volume manufacturing environment and, hence, has been found to be undesirable. Accordingly, there is a need for an improved process for inspecting barrier layer placement on an ink jet print cartridge.